The UK supreme court has cleared the way for the publication of secret letters written by Prince Charles to British government ministers, declaring that an attempt by the state to keep them concealed was unlawful.

The verdict – the culmination of a 10-year legal fight by the Guardian – is a significant blow for the government, which has been battling to protect Charles from scrutiny over his “particularly frank” interventions on public policy.

[...]

Delivering the verdict, Neuberger said: “The supreme court dismisses the attorney general’s appeal. The effect is that the decision of the upper tribunal, that the advocacy correspondence is disclosable under the Freedom of Information Act and, in the case of environmental material, the environmental information regulations 2003, stands.”

He said it was not reasonable for Grieve to issue the veto “simply because, on the same facts and admittedly reasonably, he takes a different view from that adopted by a court of record after a full public oral hearing”.

He added: “There is no clear or specific suggestion anywhere in the [Freedom of Information Act] that it is intended that [a veto] should enable a member of the executive to over-ride a judicial decision.”

In other words, the rule of law trumps the monarchy (or, as an earlier judge put it, "the proposition that the executive obey the law as a matter of grace and not as a matter of necessity [is] a proposition which would reverse the result of the Civil War").

David Cameron, who has already changed the law once to prevent any further disclosure of unconstitutional monarchical lobbying, is threatening to change it again. But its the last day of parliament before the election and the Tories are too busy infighting (over, I should note, a Speaker who took their role seriously rather than simply being a pawn of the executive), and they have to get the agreement of not one but two houses. So its unlikely that he'll be able to carry through with his threat. So, we can either expect to see the "black spider memos" released, revealing the true extent of Charles Windsor's lobbying pre-2006 - or we will see him jailed for contempt of court.

The full judgement is here. Paragraphs 51 - 59 is where the action is, and are a strong lesson on the rule of law.